Question: If $9a + 2b + 3c = 1$ and $2x + 3y = 7$, what is $-24y + 16b + 24c - 16x + 72a$ ?
Answer: $= 72a + 16b + 24c - 16x - 24y$ $= (8) \cdot (9a + 2b + 3c) + (-8) \cdot (2x + 3y)$ $= (8) \cdot (1) + (-8) \cdot (7)$ $= 8 - 56$ $= -48$